Technical Field
The present invention is related to a fan. More particularly, the present invention is related to a centrifugal fan and the impeller thereof.
Description of Related Art
With the advent of the electronic devices toward higher efficiency and smaller size, the temperature of the electronic device in operation gets higher, which influences the reliability of the electronic devices. Therefore, a fan is usually installed in the electronic device for dissipating heat.
The centrifugal fan is one of the popular heat dissipation devices. This fan utilizes inlets on the upper surface and the lower surface to inhale the air, and utilizes an outlet on the lateral surface to discharge the air, so as to dissipate the heat.
When the centrifugal fan is working, the blades or the ribs in the fan passing through a particular location causes a periodical variation in air pressure. The frequency of the air pressure variation relates to the amount of the blades, the amount of the ribs in the fan, and the rotation speed of the fan. The sound volume of the centrifugal fan at this frequency is particularly high, which is uncomfortable for the user of the electronic device and thus is regarded as noises.